Motherboard repair - it might be possible.

Thread Starter

Ivan Ivanov

Joined Apr 23, 2015
17
HI all :)

I'd like to direct this question to those of you, who has some experience in repairing VRMs of motherboards...

OK, I have a Rampage II Extreme I burned about 2 years ago. It was solely my fault. I tried to mount a cooler in a DIY manner, and the result was: scraped protective lacker, a trace shorted to the ground, a little smoke and smell of burned plastic, and finally a dead PC.

However now I have a perfect use case for that PC. Also I'm itching to see if I could pull it off. I know it's not worth the effort. The CPU might be dead as well so it could all be in vain. Although I do have reason to believe it survived.

The PC did not die immediately and it wasn't a flashy death. Nothing popped, there were no sparks. I turned it on (after I had done the nuisance) and it posted. I entered the BIOS and saw that two of the RAM modules are not recognized. Then the PC shut down on it's own as it was in the BIOS. I turned it on again and then I felt the smell. It shut down again and that was it... I saw the smoke but is was too little for me to see exactly where it was coming from.

That was 2 years ago...

Now. There is no visible damage, no disintegrated MOSFETS, no blackened spots, nothing. The diagnostics I've done so far: Using the buzzer of my multimeter I was able to check all MOSFETs in in the VRMs of the CPU and RAM.
As I touch the probes to Drain-Source of any MOSFET I hear a short beep (less than a second) and then it stops. I can also see the reading of the multimeter increases. The "resistance" is increasing. Obviously a capacitor is charging. I consider this to be normal. All MOSFETs responded this way, but three of them. Those three show a constant whine between drain and source. I think those are the culprits. It's the same between drain and ground, that shouldn't be right. They are part of the memory powering VRM. I know that because there is an inscription on the board. And it makes complete sense, because the two modules that weren't found right before the PC died ... Supposedly because they weren't receiving any power. So I think if something should've burned out with the board that should've been a RAM module or two not the CPU?! Of course I can't be sure.

... Oh and all the RAM modules were fine, they all work in other PCs ever since.

I was able to follow the shorted trace (not shorted any more, it was shorted by a washer with a sharp edge that scraped the lacker) to a PWM chip. I couldn't find the datasheet of that one. My theory is that the short circuit obstructed the normal operation of that chip that supposedly drives those MOSFETs, therefore those three remained constantly open and thus they burned. Should be something of that sort...

So my question is should I just replace those MOSFETs or should I continue to investigate for other damaged components?
Or am I no the right track at all?!

Thanks a lot in advance :)
 

dl324

Joined Mar 30, 2015
12,918
So my question is should I just replace those MOSFETs or should I continue to investigate for other damaged components?
Or am I no the right track at all?!
Not worth the bother.

Even if you replaced all visibly damaged parts, you have no way of exercising all of the logic on the board. It might appear to work, only to fail after some bit of logic that wasn't visibly damaged gets exercised and causes a crash or other problem. The worst problems would be those that cause a data corruption (e.g. writing to disk) that aren't detected immediately.
 
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